Apparatus for the detection of displacements



A ril 25, 1939. R, GUNN 2,155,419

APPARATUS FOR THE DETECTION OF DISPLACEMENTS s Sheets-Sheet 1 Filed Dec. 4, 1936 IN VE NTOR Boss Gunn $5M. arvmw ATTORNEY April 25, 1939. R. GUNN 2,155,419

APPARATUS FOR THE DETECTION OF DISPLACEMENTS Filed Dec. 4, 1936 3 Sheets-Sheet 2 I I I I I mmnm INVENTOR B055 Gunn ATTORNEY April 25, 1939.- N 2,155,419

APPARATUS FOR THE DETECTION OF DISPLACEMENTS Filed Dec. 4, 1936 3 Sh eetg-Sheet 3 i wlhllllllljlh'l ILEE mlllllllll -l l l l l l l INVENTOR R055 Gann ATTORNEY Patented Apr. 25, 1939 UNITED STATES PATENT OFFICE APPARATUS FOR THE DETECTION OF DISPLACEMENTS REISSUED FEB 2 1940 (Granted under the act of March 3, 1883, as

amended April 30, 1928: 370 0. G. 757) My invention relates to an apparatus for detecting displacements and more particularly to an electrical apparatus for the remote and substantially instantaneous detection or measurement of mechanical displacements.

In carrying out my invention, I employ a space discharge device which includes at least a cathode and a movable anode and provide means responsive to the displacement to be detected or measured for imparting movement to the said anode. Any movement imparted to the anode results in a change in the average internal resistance between the anode and cathode with attendant change in the space current through the space discharge device. By connecting the space discharge device in a proper circuit and providing suitable indicating or recording means, a displacement of any desired character or magnitude may be detected or measured. Various types of novel space discharge devices and circuits may be advantageously employed in carrying my invention into effect all of which will be pointed out more in detail hereinafter.

The apparatus of my invention is capable of detecting or measuring high frequency periodic or non-periodic mechanical displacements, whose values closely approximate the wave length of red light and by the employment of suitable auxiliary means is readily adaptable to detecting or measuring displacements even to as great a value as a foot. Because of its simplicity, ruggedness, practicability and extreme sensitivity, my apparatus has a wide field of application. As fllustrative of its many uses it may be employed for detecting or measuring mechanical or elastic vibrations such as occur in bridges, buildings, various machinery and other structures; for detecting or recording earthquakes, either natural or such as are produced as incidental to gee-physical exploration; for detecting or measuring elastic deformation such, for example, as would occur in a ships structure or a propeller shaft; for detecting or measuring angular displacements; and for detecting or measuring instantaneous liquid or gaseous pressures. Many other uses will readily occur to those skilled in the art.

With the foregoing preliminary discussion of view, it is an object of my invention to provide a simple, rugged and eiiective electrical apparatus for detecting or measuring periodic or non-periodic mechanical displacements of either large or small magnitude.

It is another object of my invention to provide an electrical apparatus for detecting or measuring mechanical displacements wherein any change It is another and still further object of my in- 10 vention to provide new and novel space discharge devices for incorporation in my detecting or measuring apparatus but which, however, are susceptible of being advantageously used in other environments. 1

Other objects and many of the attendant advantages of this invention will be readfly appreelated as the same becomes better understood by reference to the following detailed description when considered in connection with the accom- 20 panying drawings, wherein:

n Fig. 1 discloses one embodiment of my inven- Fig. 2 discloses an alternative embodiment of my invention employing a diil'erent space dis- 25 charge device and circuit arrangement;

Fig. 3 depicts a further modification of my invention differing over that of Fig. 2 m'incipally in the employment of a grid circuit:

Fig. 4 shows another form that my invention 30 may take and wherein a differential galvanometer is employed;

Fig. 5 depicts a still further embodiment of my invention which is especially designed for detecting or measuring angular displacements;

FlFigs. 6 is a sectional view taken on the line H,

Fig. 7 shows another modification of my apparatus employing two cathodes in the space discharge device thereof and an amplifier for am- 40 pulliftying any voltage diil'erential of the bridge cir- Figs. 8 and 9 represent difierent embodiments of my invention wherein the displacement of the movable electrode or electrodes of the space dis- 45 charge device is controlled by suitable external magnetic means; and

Fig. 10 depicts a modification of my invention suitable for the detection or measurement of fluid pressure.

Before proceeding with a detailed description of the various embodiments of my invention it is deemed advisable at this point in the interests of clarity and in order to avoid needless repetition in the subsequent description to make certain gen- 55 eral remarks concerning the space discharge devices and circuits employed in my apparatus. As pointed out hereinbefore, each space discharge device includes at least one cathode which serves as a source of electrons. A cursory examination of the drawings will show that all cathodes have been depicted therein as of the thermionic type, the heating thereof to insure electron emission being accomplished either directly or indirectly bya suitable source of electromotive force. I wish to emphasize in this connection, however, that I do not desire to be restricted to this type of cathode since cathodes. which emit electrons due 'to bombardment by rapidly moving ions, electrons, or metastable atoms and are said to be secondarily emissive, or photo-electric cathodes, or cold or non-thermionic cathodes which spontaneously emit electrons due to treatment thereof by a radioactive substance, all will serve the purpose of my invention equally well. As for the thermionic cathode, it may be fabricated of a pure metal, be oxide-coated, be of a metal provided with an adsorbed monatomic film of one of the electro-positive metals or be of any other type known to the art. The envelopes of my space discharge devices which are fashioned from any of the materials known to the prior art and serve to enclose the electrodes may be evacuated to produce a high vacuum and thus insure a substantially pure electron discharge or may alternatively be provided with a suitable filling of a gas or vapor, gases or vapors, or mixtures of gases and vapors at a selected pressure or pressures to insure the desired operating characteristics.

Many of the circuits'employed in various embodiments of my invention take the form of a Wheatstone bridge in which three electrodes of a space discharge device are connected to form two branches thereof, the remaining two branches being formed by two variable resistances which serve to effect a balancing of the bridge circuit prior to any detecting operation. Means responsive to the displacement to be detected or measured serve to impart movement to at least one of the said three electrodes to cause simultaneously thereamong a decrease in electrical resistance between the first and second electrodes and an increase in electrical resistance between the first and third electrodes, thus causing an unbalancing of the bridge circuit which is indicated by a suitable indicating or recording device. It is, of course, apparent that the indicating device may be suitably calibrated to indicate not only the magnitude of the displacement but also its direction.

The basic principle underlying my invention may be best appreciated by considering the embodiment disclosed in Fig. 1 of the drawings. There is shown depicted in this figure an envelope I of a space discharge device which includes as part thereof a flexible bellows-like metallic or glass extension 2 to the end of which is rigidly secured the anode 3 by means of the lead-in wire 4. A cathode 5, which may be of a thermionic type, is heated to an electron emissive temperature by the source of electro-motive force 6. The plate circuit of the space discharge device includes the source of electro-motive force 'I and an indicating device 8 which may be a milliammeter. The force, pressure or displacement to be detected is represented schematically by the arrow 9. A small spring and anvilili are arranged to return the extension 2 of the space discharge device to its initial and desired position of rest upon removal of any actuating force or pressure. It is evident that the mounting of the anode I is such that the application of a force or displacement 9 as shown will change the mean spacing between the anode 3 and cathode 5, this displacement of the electrodes being made possible by reason of the flexible bellows-like extension 2.

It is well-known in the vacuum tube art that with a given plate potential the space current density varies in a non-linear manner with the electrode spacing and increases rapidly as the spacing between the anode and cathode structures is reduced. This fact was first established by Child and is known as Child's law. Thus, the average internal resistance between the anode -3 and cathode 5 is a definite and reproducible function of the spacing between these electrodes. which spacing is controlled by displacing the end of the flexible extension 2 by a force or pressure 9. It is therefore evident that any change in spacing between the electrodes 3 and 5 will result in a change in space current, the indicating device 8 reading more or less depending upon whether the spacing between the electrodes is decreased or increased. Hence, any departure from a predetermined and initial reading of the milliammeter serves to detect a displacement, the

magnitude of which is easily ascertainable by suitable calibration of the milliammeter or indicating means 8. While the apparatus of Fig. 1 is an entirely operative and useful structure it does, nevertheless, possess certain inherent disadvantages. If, for example, the emissivity of the cathode 5 is in any manner impaired or the value of the electromotive force of either sources I or 1 changes, this will be evidenced by first order changes in the plate current indicated by the milliammeter 8. If, then, the indicating means has been previously calibrated for a fixed electron emissivity and fixed values of electro-motive forces, it is evident that the indicating means 8 will now give inaccurate and false readings. In order to avoid any such diiilculty as might be encountered in using the apparatus of Fig. 1, I provide different tube structures and circuit arrangements as will be pointed out hereinafter. In Fig. 2 of the drawings there is shown a space discharge device and circuit arrangement which avoids the difficulties that may be encountered with the apparatus of Fig. 1. In this figure ll denotes the envelope of the space discharge device which like that of Fig. 1 has at one end thereof a flexible metallic or glass bellows-like extension l2 to which are secured and insulated from each other the two anodes l3 and I4 supported by their respective lead-in wires i5, Ii. The cathode i! which may be of a thermionic type is heated to an electron emissive temperature by the battery IS. The insulated lead-in wires i5 and I6 are connected in a bridge circuit which includes the two balancing resistances l9 and 20. It is thus seen that the bridge circuit includes four arms or branches, two of which are constituted by the resistances between the anode l3, cathode l1, and anode i4, cathode H with the resistances i9 and 20 heretofore mentioned forming the remaining two branches. The indicating device 2| which may be a milliammeter is placed across one diagonal of the bridge and the plate potential or source of elec-- tro-motive force 22 connected across the remaining diagonal. Asmall spring and anvil 23 again serve to return the extension or projection l2 of the space discharge device to its initial and desired position of rest upon the removal oi. any actuating iorce. It now the end of the extension of projection I2 is displaced in any manner, such as for example by the indicated micrometer 24, the anode it will move toward the cathode l'l while simultaneously'the anode it will move away from the cathode, this movement of the electrodes occurring due to the fact that the anodes i3 and I5 are rigidly secured to the end of the projection or extension i2 by means of the lead-in wires II and it. The former electrode movement tends to decrease the internal resistance between the anode II and cathode i1 and the latter has a tendency to increase the resistance between the anode l5 and cathode ll. 11, then, the bridge be balanced by a suitable adjustment of the variable resistances i5 and prior to the application or a iorce by the micrometer 24, the bridge will now be unbalanced in both its arms by the displacement of. the micrometer. It is at once evident that any unbalancing of the bridge circuit will be indicated by the milliammeter 2i and that "the direction of the indication of the milliammeter 2i will indicate the direction of the displacement. The apparatus of Fig. 2 possesses important advantages over that disclosed in Fig. 1. For example, if the emission of the cathode I1 is in any manner impaired or if the values of the electro-motive forces l8 and 22 change, these changes or variations in emissivity and voltage will afiect the plate circuits in the bridge equally and to the first order at least. These variations or changes, however, will not be indicated by the milliammeter II. It is thus clear that the apparatus of Fig. 2 provides a very rugged and practicable structure for indicating or measuring displacements.

The apparatus shown in Fig. 3 is a variation of that shown in Fig. 2. In this figure the envelope 25 of thespace discharge device is provided at one end thereof with a flexible metal seal 25 sealed to it in any manner known to the prior art, the said seal 25 having secured thereto the tubular metallic member 21 supporting the anode leads 28 and 25. The anode lead 25, as shown, supports the anode 30 and is hermetically sealed to and insulated from the tubular member 21 by means of the insulating plug ii. The metallic tubular member 21 besides serving to impart movement to the anodes and 32 serves also as a current conductor. The cathode 33, which may be of a thermionic type, is heated to an electron emissive temperature by the battery 34 and is surrounded by a grid 55 which is connected to a suitable source or biasing voltage 35. The space discharge device 25 as in the preceding figure is connected in a bridge circuit to form two branches thereof, the remaining two branches being constituted by the variable resistances 31 and 58. Any convenient source of electromotive force 35 serves to supply the current for energizing the bridge circuit. The tubular member 21 with the anodes 30 and 32 rigidly secured thereto is moved by any means such as the indicated micrometer 40. An oscillographic element ll is shown in the bridge circuit to emphasize the fact that periodic or rapid displacements of the small projecting tube may be indicated and recorded by photographic or other methods. The essential diflerenee of the apparatus of Fig. 3 over that of Fig. 2 resides in the employment of a grid structure 55 and a biasing battery 36. This arrangement can be made somewhat more sensitive than that of Fig. 2 and balancing of the bridge is somewhat more convenient. The

apparatus 0! Fig. 3, however, also employs the fundamental principle of a change in plate resistance attending the simultaneous movement of the anodes ll and 52 as a result of the applicagionzoli' a pressure or force to the tubular mem- Fig. 4 shows another modification of my apparatus wherein 52 denotes the envelope enclos ential galvanometer with an appropriate balancing resistance 49 is connected in the plate or bridge circuit of the space discharge device, a source of electromotive force 50 serving to energize the circuit. The windings 5i and 52 of the difierential galvanometer are, of course, connected so that they annul each other and if the current increases in one coil and decreases in the other, the deflection will be increased due to both causes. The balancing resistance 49 connected across the coil 5| permits the employment of the diiferential galvanometer as a null instrument. Again, a spring and anvil are schematically represented at 53 to return the tubular member 41 to its initial and desired position of rest upon the removal of any actuating force. Anvils 54 and 55 and a test object 55 suggest one use of the apparatus which is applicable to the modifications previously described and to be described hereinafter. Thus, for example, it the test object 55 is a standard test piece and is introduced between the anvils 54 and 55 as shown the bridge may be balanced so that the galvanometer 48 will read some predetermined value. Then as object 55 is removed and comparison objects are introduced in place thereof, the galvanometer or indicator 45 will read more or less than the value established for the standard test piece, thus showing that the object under test is greater or less in diameter than the standard. The galvanometer 48 is readily calibrated and standardized with the result that the exact amount of departure of any test piece from that of the standard can be easily and quickly determined.

Fig. '5 and 6 illustrate a still further modification of my apparatus which is especially designed for indicating or measuring angular displacements. In this embodiment 51 designates the grid structure surrounding the cathode 55 and as shown consists of a plurality of conductors 59 which are arranged more or less parallel to the electron emissive cathode. The anode or plate structures illand ii are also each made of pinrality of conductors which are parallel to those of the grid and substantially parallel to the cathode and are so arranged that when the conductors of the anode 60 (see Fig. 6) are behind the grid conductors and thus substantially fully shielded from the cathode, the conductors of the anode 5| are substantially fully exposed to the cathode. The envelope of the space discharge device includes an insulating portion 62 to which is sealed a metallic portion 63 having a part thereof terminating at 64 which is flexible and to which twisting or torsional movements may be imparted. Rigidly secured to the part or extension 54 is a tubular metallic member 55 in which the lead-in wires of the anodes l and H are'insulatingly supported and hermetically sealed by the insulating-plug 00. It is evident that any angular movement of the extension 04 will result in rotary or angular movement of the anod 40 and II. A suitable source of electromotive force 41 serves to bias the grid while the remaining electrodes of the space discharge device are connected in a bridge circuit which includes the variable resistances 04 and 09 and the voltage source I0 for energizing the same. As in the previous embodiments of my invention I a suitable indicating device II is provided for detecting any differential voltage in the bridge circuit. The manner of operation of the apparatus in Fig. is believed to be clear. Thus if any torsional movement is imparted to the flexible extension 04 by any means whatsoever rotary movement of the anodes 00 and II will result. Assuming that the initial positions of the anodes 00 and 0| are shown in Fig. 6 if the movement is in the direction indicated by the arrow the conductors of the anode 00 will be exposed more and more to the cathode 54 while simultaneously the conductors of the anode 0| will be moved progressively from their exposed positions to the cathode to positions where they are shielded by the grid conductors. If the bridge be balanced prior to the initiation of any movement it is clear that the angular displacement of the anode 00 will result in an increased current flow thereto while the current to the anode 0| is decreased. Since movement of the anodes causes a variation in the tube resistances with attendant variation of currents in the bridge circuit it is evident that the bridge is now unbalanced and that any difi'erential voltage thus caused is indicated by the indicating device "II. In this manner it is possible to indicate or measure angular displacements. 1

In the modification of Fig. '1, I2 indicates the envelope of the space discharge device to which is sealed the flexible metallic cap I5 for movably mounting the anode 14. The anode as shown is interposed between two cathodes I5 and 16 of the indirectly heated type which are heated to an electron emissive temperature by the resistance units 11 and It energized by the battery 10. A small spring and anvil 00 serve to return the anode to its initial and desired position of rest, movement being imparted to the anode, for example, by the test piece 0| which is shown interposed between the anvil l2 and micrometer 03. The space discharge device of Fig. 7 has certain advantages over those previously, described in that it is not necessary to insulate two moving lead-in wires for the anodes and as in the previous embodiments is connected in a bridge circuit which includes ahe variable resistances 04 and 05 and a suitable source of electro-motive force 06. The apparatus depicted in Fig. '1, however, difl'ers over those previously described in that any diiIerential voltage produced in one diagonal of the bridge circuit is amplified, this being accomplished by connecting parts of the bridge circuit as shown to grid 06 and an indirectly heated cathode of an amplifier tube 00. This amplifier tube in turn forms one branch are secured to relatively flexible lead-in wires 00 and 01, a cathode 90, which may be of a thermiomc type, being interposed between the said anodes. The electrodes of the space discharge device are connected in a bridge circuit to form two branches thereof, the remaining vtwo branches being formed by the variable resistances 09 and I00 and energized by a suitable source of electro-motive force IOI. As in the previous modifications an indicating device I02 serves to indicate or measure any displacement of the anodes 04' and 95 with respect to the cathode 80. The position of the anodes within the space discharge device is controlled by any suitable,

external magnetic means such as, for example, a permanent magnet I03. The position of the magnet I03 is controlled by the displacement which it is desired to detect or measure, it being apparent that the magnet may be moved in a desired manner. Thus, for example, rotation of the magnet I03 about its axis of symmetry will produce a displacement of the magnetic anodes within the tube in such a way that angular displacements may be readily indicated on the milliammeter or indicating device I02. I

Fig; 9 illustrates another form which my apparatus may take. In this embodiment two thermionic cathodes are employed, one of which isdesignated in general by the numeral I04 and made in two portions I04 and I04", the remaining cathode I05 being similarly constructed and consisting of the parts I05 and I05". The cathodes I04 and I05 are heated to an electron emissive temperature by the respective sources of electromotive force I06 and I01. The anode is shown at I00 as a magnetized body and is interposed and mounted for rotation between the cathodes. The space discharge device as in the previous embodiments is connected in a bridge circuit to form two branches thereof, the remaining two branches of "which are constituted by the variable resistances I09 and I I0 which are energized by the source of electro-motive force III. the bridge is indicated by a suitable indicating device III. As in the modification of Fig. 8 the position of the anode I00 is controlled by any suitable external magnetic means such as, for

example, the magnet 3, the position of the said.

anode with respect to a selected initial position being indicated by the indicating device III.

One important application of my apparatus is to the measurement of instantaneous fluid pressures such, for example, as the changes in pres-.

surcin the cylinders of a Diesel engine when it is in operation. Fluid pressures of any character may be conveniently indicated or measured by the apparatus shown in Fig. 10 of the drawings. In this embodiment I I4 designates a vessel of any suitable insulating material apertured at points H5 and H6 and transversely of which there extend two flexible partitions H1, H8 which may be of metal to thus provide upper and lower chambers H9, I and an intermediate hermet-.

Any difierential voltage in a diagonal of.

ically sealed chamber I2I. Anodes I22 and I23 are electrically connected to and supported by the respective diaphragms or partitions H1, Ill,

"I are connected to form two branches of a bridge circuit of which the remaining two branches are constituted by the variable resistances I25 and I26. Any suitable indicating device I2l serves to indicate any difierential voltage in the bridge circuit which is energized by the source of electro-motive force I28. The chambers I I9 and I20 serve as receptacles for the fluid, the pressure of which is to control the displacements of the diaphragms III and H8. It is evident that any pressure applied to the diaphragm Ill will cause a displacement thereof thus decreasing the spacihg between the anode I22 and the cathode I24 with attendant unbalancing of the bridge circuit as evidenced by an indication of the indicating means I21. The indication of the indicating means I21 will of course be proportional to the displacement of the diaphragm Ill. The diaphragm Ill which is electrically connected in the bridge circuits and to the anode I23 is introduced for two reasons. It serves as a means for balancing out irregularities in emission of the cathode or any voltage variation in the sources of electro-motive force but is primarily intended to correct for any changes in barometric pressure. As pointed out hereinbefore, if the diaphragm III is subjected to fluid pressure the displacement of the diaphragm will be proportional to the pressure exerted upon it. If, for example, the apparatus is employed as a fuel gauge in aircraft, operations at high altitudes will reduce the displacement of the diaphragm Ill and in order for the indicating device I2'I to read the proper pressure-head the anode I23 must be displaced a distance equal to the distance displaced by the anode I22 due to the increased altitude. To insure a displacement of the anode I22 and hence a correct and accurate reading of the indicating device I2'I the diaphragm 'I I8 is provided. It is clear that the apparatus of Fig. 10 may be used to indicate diilferential pressure.

All the novel features of my space discharge devices are claimed in this application, the features of novelty of my system or apparatus as a whole, however, being claimed in application Serial Number 114,112 filed concurrently herewith.

The invention herein described and claimed may be used and/or manufactured by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. A space discharge device comprising an envelope enclosing at least three electrodes, said electrodes including two independent and immovably mounted cathodes and one movably mounted anode, the said three electrodes being mounted for simultaneous cooperation and being disposed to clause an increase in one anode cathode resistance simultaneously with a decrease in a like resistance, and means operable to impart movement to said anode to cause a change in spacing between said anode and cathodes.

2. A space discharge device comprising an envelope enciosing at least three electrodes, said electrodes including at least one immovably mounted, cathode and at least one movably mounted anode, the said three electrodes being mounted for simultaneous cooperation and being disposed to cause an increase in one anode cathode resistance simultaneously with a decrease in alike resistance, and means operable to impart rotational movement to at least one of said three electrodes to cause simultaneously thereamong a decrease in electrical resistance between the first and second electrode and an increase in electrical resistance between the first and third electrode.

3. A space discharge device comprising an envelope enclosing at least three electrodes, the said three electrodes being mounted for simultaneous cooperation and being disposed to cause an increase in resistance between two electrodes simultaneously with a decrease in a like resistance, and means operable to impart rotational movement to at least one of said three electrodes to cause simultaneously thereamong a decrease in electrical resistance between the first and second electrodes and an increase in electrical resistance between the first and third electrodes.

4. A space discharge device comprising an envelope enclosing a cathode, grid and two anodes, the said electrodes being mounted for simultaneous cooperation and being disposed to cause an increase in one anode cathode resistance simultaneously with a decrease in alike resistance, and means operable to impart rotational movement to said anodes.

5. A space discharge device comprising an envelope enclosing a cathode, grid and two anodes, the said grid and anodes each being formed of a plurality of longitudinally extending conductors with the grid surrounding the cathode, the said electrodes being mounted for simultaneous cooperation and being disposed to cause an increase in one anode cathode resistance simultaneously with a decrease in a like resistance, and means operable to impart rotational movement to said anodes.

6. A space discharge device comprising an envelope enclosing a cathode, grid and'two anodes, the said grid and anodes each being formed of a plurality of longitudinally extending conductors which are arranged such that when the conductors of one anode are substantially fully shielded by the grid conductors from the cathode the conductors of the other anode are substantially fully exposed to the cathode, and means operable to impart rotational movement to said anodes to thereby vary the positions of the anode conductors with respect to the grid conductors.

7. A space discharge device comprising an envelope enclosing two independent spaced electron emissive cathodes and an anode interposed therebetween, the said three electrodes being mounted for simultaneous cooperation and being disposed to cause an increase in one anode cathode resistance simultaneously with a decrease in a like resistance, and means operable to impart movement to said anode to cause simultaneously a decrease in spacing between the said anode and first cathode and an increase in spacing between the-said anode and the second cathode.

8. A space discharge device comprising an envelope including at each end a flexible metallic diaphragm, an anode electrically connected to and supported by each diaphragm and a cathode interposed between said anodes.

9. A space discharge device controllable by fluid pressure, comprising a vessel, a plurality of flexible partitions extending across said vessel to form therewith end chambers and an intermediate chamber, an anode supported by each of said flexible partitions for movement 'within said intermediate chamber and a cathode interposed between said anodes, the said end chambers constituting receptacles tor the fluid medium, the pressureot which is to control the characteristics o; the space discharge device.

10. A space discharge device. controllable by fluid pressure, comprising a vessel, a plurality of flexible partitions extending across said vessel to tow therewith a plurality of chambers, an anode supported by each of said flexible partitions for movement within one of said chambers, and a cathode interposed between said anodes, the remaining chamber constituting a receptacle for the fluidmedium, the pressure of which is to control the characteristics of the space discharge device.

11. A space discharge device controllable by fluid pressure, comprising a vessel, a plurality of partitions extending across said vessel and torming therewith a plurality oi. chambers one of which is hermetically sealed, one of said partitions being flexible, an anode supported by said flexible partition for movement within said hermetically sealed chamber and a cathode cooperating therewith, the remaining chamber constituting a receptacle for the fluid medium, the pressure of which is to control the characteristics of the space discharge device.

12. A space discharge device controllable by fluid pressure, comprising a vessel, a plurality of partitions extending across said vessel and forming therewith a plurality of chambers, one oi which is hermetically sealed, one of said partitions being flexible, an anode and cathode electrode mounted for cooperation within said hermetically sealed chamber, one of said electrodes being supported by the aforesaid flexible partition, the remaining chamber of said device constituting a receptacle for the fluid medium, the pressure of which is to control the characteristics o! the space discharge device. 

